In many circuits, a relatively large valued capacitor is desired. However, to manufacture the relatively large valued capacitor in, and on, an integrated circuit (or chip), normally requires that an unduly large portion of the available area of the integrated circuit be devoted to the capacitor. Accordingly, relatively large valued capacitors may be required to be connected externally to the integrated circuit. Externally connecting components (e.g., a capacitor) to the integrated circuit may present several problems including, but not limited to, decreased reliability, increased signal noise, and worse matching between components.
One approach to the problem of insufficient on-chip capacitance may include the use of a known capacitance multiplication circuit (100) as shown in FIG. 1. The capacitance multiplication circuit (100) includes an amplifier circuit (102) and a resistor R2 connected between a node of the amplifier circuit (102) and VIN. A capacitor C1 is connected between the node and a reference voltage potential, in this example, a ground voltage potential. The amplifier circuit (102) is arranged as a unity gain amplifier. Another resistor R3 connects between a another node of the amplifier circuit (102) and VOUT. The amplifier circuit (102) ensures that the voltage drop across the resistor R3 is equal to the voltage drop across the resistor R2. The effective capacitance of the capacitance multiplication circuit (100) is equal to C1 times (R2+R3)/R3. Thus, by making R2 larger than R3, the effective capacitance is much large than the capacitance of C1.